Density and aspect ratio controlled MgZnO nanowire arrays by spontaneous phase separation effect

This study reports a simple method of controlling the density and aspect ratio of vertically arrayed ultra-slim MgZnO nanowires developed through the formation of selective crystalline seeds by metal-organic chemical vapour deposition at a high growth temperature. The thin multilayer structures with an amorphous MgO layer and amorphous and single crystal MgZnO layers developed by self-phase separation between the nanowires and substrates played a vital role in the growth of the MgZnO nanowires. The dimensional competition between the Zn-rich seed crystals and Mg-rich amorphous layers induced by spontaneous phase separation at different Mg fluxes determined the density and aspect ratio of the nanowires. Based on the thermodynamical calculations and microstructural characterizations, the growth procedure and models for the evolution of the ultra-slim nanowires on the Si substrates are proposed for different Mg flow rates.